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On the Chemistry of Pyrrole Pigments. 46 1 Phytochrome Model Studies: The Tautomerism at N 22 —N 23 of Unsymmetrically Substituted Bilatrienes‐ abc and 2,3‐Dihydrobilatrienes‐ abc
Author(s) -
Falk Heinz,
Grubmayr Karl,
Magauer Karl,
Müller Norbert,
Zrunek Ulrich
Publication year - 1983
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198300027
Subject(s) - chemistry , tautomer , phytochrome , pigment , pyrrole , computational chemistry , stereochemistry , organic chemistry , botany , red light , biology
A set of model compounds substituted with methyl groups in positions 7,8,12 and 13 were prepared to elucidate the tautomerism within the pyrromethene moiety of unsymmetrical bilatrienes and of 2,3‐dihydrobilatrienes‐ abc . Configurational and 1 H‐NMR signal assignments were achieved using NOE difference spectra, coupling phenomena and comparison to the spectra of compounds substituted with ethyl groups in strategic positions. By application of resolution enhancement and the COSY‐technique a characteristic coupling pattern between the methyl groups of a pyrrole ring which is different from the one observed for the pyrrolenin ring could be documented using derivatives with fixed tautomeric structure (N‐methylation). All unsymmetrical bilatrienes and 2,3‐dihydrobilatrienes‐ abc investigated are shown to be single tautomers — the position of the proton (N 22 , N 23 ) obviously is governed by an optimisation of intramolecular hydrogen bonding.